Vera Rubin obituary
Vera Rubin once tweeted: "Don't let anyone tell you that you aren't good enough. My science teacher once told me I wasn't good enough for science and look at me now." In the 1970s and early 80s Rubin, who has died aged 88, established that the stars in the outer regions of galaxies move at similar speeds to those in the middle, a result that led to the hypothesis that most of the universe is invisible, the cosmos filled with "dark matter", mysterious stuff whose nature is still unknown. During recent years she became a popular favourite for a Nobel prize, but never received the accolade. Having battled sex discrimination throughout her career, she became an inspiration for women in science.
In the outer regions of the solar system, far away from the sun where the force of its gravity is more feeble than hereabouts, planets move more slowly than the Earth. Were Uranus to move as fast as us, it would escape from the solar system entirely, its centrifugal thrust too large for the weakened inwards gravitational pull from the sun. This has been understood since Isaac Newton in the 17th century, and is a cornerstone of Einstein's general relativity: bodies orbiting a central mass will have speeds that fall in proportion to the square root of their distance from the centre.
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